Dye receptive filament



United States Patent 3,128,221 DYE RECEPTli E FELAMENT Juan Antonio Flores, Chattanooga, Tenn., assignor to E. I. du Pont de Nemours and Company, Wilmington, Deb, a corporation of Deiaware Filed Feb. 19, 1962, Ser. No. 173,892 9 Claims. (Cl. 161-175) This invention relates generally to synthetic linear polycarbonamides and, more particularly, to a copolyamide of poly(hexamethylene adipamide) which, when spun and otherwise processed in a conventional manner, yields fabrics having a unique combination of rapid dyeability and a high level of retained physical properties as compared to fabrics produced from a 66 nylon homopolymer.

Poly(hexarnethylene adipamide) is Well known for superior textile properties such as tenacity, resilience, wear resistance and the like. However, it is also known that textile products produced therefrom do not dye rapidly and uniformly. Previous attempts to remedy this defect by copolyrnerization with other polyamide-forming components have resulted in an intolerable loss in physical properties such as tenacity and yarn stability.

The most important object of the present invention is to provide a copolyamide textile filament having physical properties substantially equivalent to those of 66 nylon as well as a high dye absorption rate and improved uniformity of dyeing.

The above and other objects are accomplished in a textile filament spun from a synthetic linear copolyamide consisting essentially of from about 91-95% by weight of the repeating unit This copolyamide is readily prepared under conventional polyamidation conditions and no special equipment is required. Likewise, it can be spun and drawn on conventional equipment. The tensile properties of the co polyamide filament are substantially equivalent to 66 nylon as will be shown hereinafter. In contrast, the rate of dye penetration is nearly ten times as rapid as for a corresponding filament of 66 nylon.

The appended drawing consists of a graph showing the effect of copolymer composition on the tenacity of and dye penetration into the copolymer filament of the present invention.

The dye rate, as reported herein, is measured by immersing a skein of yarn weighing 15 grams in a test tube containing a solution of 0.001 gram per milliliter of the cobalt complex dye disclosed in Example III of German Patent 743,155 (1943) and known as Perlon Fast Red 3B5. The solution is maintained at the test temperature (55 C. in the following examples). The test tube is placed between a light source and a photocell and the light absorption of the solution is measured as a function of time, as the dye is taken up by the fiber. The reciprocal of the time elapsed until the absorption rate has dropped to one half the original value is a measure of the dye rate.

The uniformity of dye penetration is determined by irrunersing skeins of test yarn in a bath containing 1 gram of Color Index Number Acid Blue 113 in 4 liters of water, maintained at a temperature of 80-90 C. The amount of dye is in excess of that required for saturation dyeing.

After four hours in the bath, the skeins are removed, rinsed, dried and cross-sections are examined under a microscope. The percentage of radial penetration of the dye is easily measured.

The copolyamide of this invention has also been found to be particularly useful as one component of a composite filament consisting of two or more components held together in eccentric relationship as described in US. Patent No. 2,931,091. Thus, the copolyamide may be extruded in side-by-side relationship from the same orifices of a spinneret with another polymer such as 66 or 6 nylon to produce two-component structures which, after conventional quenching and drawing, may be crimped by exposure to boiling water or otherwise to produce very desirable elfects in fabrics. Alternately, sheath-core structures may be produced with the copolymer in either the sheath or core position.

All concentration percentages reported herein are by weight unless otherwise specified.

Example I A 48% aqueous solution of nylon salt is prepared. The salt component consists of 92% by weight hexamethylene diammonium adipate and 8% hexamethylene diammonium isophthalate. To the solution is added 0.03% of excess hexamethylene diamine, to serve as a viscosity stabilizer. This solution is charged to an evaporator, concentrated to about at 13 p.s.i. and transferred to an autoclave previously purged with oxygen free gas. The mixture is heated under autogenous steam pressure until 250 p.s.i. is reached, requiring about twenty minutes. Steam is then bled off while maintaining a pressure of 250 p.s.i. Heating is continued until the nominal salt concentration is about corresponding to a temperature of 230 C.

At this point, a slurry of 20% titanium dioxide in water is charged to the autoclave, in sufiicient amount to provide a final content of 0.3% of TiO in the polymer. Heating and bleeding off of steam at 250 p.s.i. are continued until the temperature reaches 245 C. At this temperature, pressure reduction is started and continued over a period of about 90 minutes until the temperature has reached 270 C. and the pressure has been reduced to atmospheric. Heating is continued for about 35 minutes at atmospheric pressure until a temperature of 275 C. is reached, completing the polymerization. The polymer is discharged by pressurizing the autoclave using oxygenfree gas and extruded as a ribbon which is then quenched, cut to one-half inch flakes and dried. The copolymer flake has a relative viscosity of 40, determined as described in US. Patent 2,385,890, and contains 8% of the poly(hexamethylene isophthalamide) (6-1) component.

The flake is charged to a grid melter and blanketed with an atmosphere of steam as disclosed by Waltz in US. Patent 2,571,975. Molten polymer issuing from the melter is pumped through a filter pack to a spinneret of 34 holes at a temperature of 288 C., extruded, quenched, steamed, contacted with a liquid finish and Wound up on a package. The filaments are then drawn four times their extruded length to form a 70 denier yarn. The dye rate (at 55 C.) of the thus-prepared copolymer yarn is determined, using the procedure previously described. When compared with .the dye rate of a similarly prepared control yarn of 66 nylon homopolymer, it is found that the copolymer yarn dyes 9.7 times as fast as the control, using the Pei-Ion" red dye mentioned above. Its tenacity is 5.16 g.p.d., compared to 5.35 for the 66 nylon control. The boil-oft shrinkage is 14.5% for the test yarn and 9.0% for the control.

When the test is repeated using a lesser amount of the isophthalate salt to make a final copolymer contain- 3 ing 6% hexamethylene isophthalamide (6-1), the tenacity is 5.32 g.p.d., the boil-off shrinkage is 13.2% and the dye rate is seven times that of the 66 nylon control.

Example II Percent Tenacity, Percent Sample No. 6-I g.p.d. Dye Penetration These results show that, within the concentration range of -9% 6-I, the tenacity of 66 nylon is retained along with uniform, complete dye penetration. At lower 6-1 concentrations, the rate of penetration drops off very rapidly whereas at higher concentrations, there is a rapid tenacity loss.

From the preceding example, it is apparent that (the percentage concentrations of 66 and 6-1 in the copolyamide filaments and yarns disclosed herein are critical. Selection of the isophthalate component is also critical; for example, if terephthalic acid is substituted for isophthalic acid, it is found that twice the acid concentration must be used in order to obtain an equal improvement in dye rate. The greater amount of terephthalic acid which is required increases polymer melt viscosity so that excessive back pressures develop, causing leaks and pack failure.

Example III 66 nylon flake having a relative viscosity of 45 is prepared in the conventional manner. The 66 nylon fiake and 66/ 61 flake, prepared as described in Example I, are melted separately in screw melters and extruded in sideby-side relation from holes in a spinneret of the type shown in FIG. 6 of U.S. Patent No. 2,931,091 to produce filaments containing about 50% of the copolymer. The spinneret has 34 holes. The filaments are quenched by passing air transversely across the filament bundle as described in U.S. Patent No. 2,273,105. The filaments are then wound into a package in the conventional manner. The filaments are subsequently withdrawn from the package and drawn to a ratio of 2.66. The yarn is then passed through a steam tube at 381 yards per minute and permitted to relax 11% as illustrated in U.S. Patent No. 3,003,222. The steam tube is 2 inches in length and is supplied with steam at 175 C. and 12 p.s.i. The yarn is then interlaced with an air jet as described in U.S. Patent No. 2,985,995 and wound into a package in the conventional manner.

When the yarn is subjected to boiling water for 15 minutes, the filaments develop about ten crimps per inch.

When the yarn is woven into a plain weave fabric, finished and dyed in the conventional manner, the resulting fabric has excellent bulk, liveliness and dryness and the excellent dyeing characteristics of the copolymer are carried over to the two-component fiber. In the latter respect, the copolymer component is the load-bearing component with the result that the same relationship illustrated in this graph for single component filaments is equally applicable to the exemplified two component filamcnts.

An advantage of the copolymer composition of this invention is that it can be processed on conventional 66 nylon equipment, with only minor changes in processing conditions. Thus, the polymer can be prepared in a conventional autoclave or it can be made in a continuous polymerizer. Due to a slightly slower reaction rate, slightly longer reaction cycles should be employed. Spinning and drawing processes are likewise conventional with the exception that a higher melt viscosity is encountered. This normally requires a filter pack with a smaller amount of fine sand. The polymer may be spun directly from a continuous polymerizer, or the flake may be melted on a grid or a screw melter may be used. Conventional drawing equipment for 66 nylon is satisfactory. The yarn may be drawn over an unheated snubbing pin or, alternatively, a heated pin may be employed. The yarn may be drawn in a single stage or in two or more stages; it may be after-treated with steam or hot air to anneal or relax the yarn. It may be bulked, crimped, twisted, false-twisted and set, according to the requirements for a particular end use.

The copolymer of this invention may contain the usual additives for polyamides, including delusterants, such as those disclosed in U.S. Patent No. 2,205,722, pigments, antioxidants, such as those disclosed in U.S. Patent No. 2,510,777 or light stabilizers, such as those disclosed in U.S. 2,887,462. It may be used as a monofilament, e.g., in hosiery, or as a multifilament yarn as disclosed in the examples. It is also suitable for extrusion simultaneously with filaments of one or more other polyamides, to form a mixed filament yarn, as disclosed more fully in the copending application of Knospe, filed on March 31, 1961, and bearing Serial No. 99,883. The filaments may be extruded as round, trilobal, ribbon or other cross sections.

In addition to its use as the sole component in various textile products, the copolymer of this invention is particularly useful as one component of a two or multicomponent filament (Example III). Thus, the copolymer may be combined with other components having a lower shrinkage potential to produce crimped or crirnpable filaments which may be used to prepare fabrics of improved aesthetics and excellent dyeability. The preferred polyamides for use in conjunction with the copolymer of this invention in multicomponent filaments are polyhexamethylene adipamide and polycaproamide. Various other suitable polyarnides and copolyamides may be selected from those disclosed in U.S. Patents Nos. 2,071,250, 2,071,253, 2,130,523, 2,465,319, 2,130,948, and 2,190,770.

The products disclosed herein are particularly useful in the production of textile fabrics, especially those which are to be dyed. The filaments may be used as such or converted to staple and used in 100% synthetic yarns or in blends with other fibers, natural, artificial, or manmade. Other variations and adaptations in the end use may be made without departing from the spirit of the present invention which is therefore intended to be limited only by the scope of the appended claims.

I claim:

1. A drawn nylon filament consisting essentially of a copolymer of polyhexamethylene adipainide and polyhexamethylene isophthalamide, there being less than 10% by weight of the isophthalamide in the copolymer.

2. The filament of claim 1 containing more than 4% by weight of the isophthalamide.

3. A drawn nylon filament consisting essentially of a copolymer of polyhexamethylene adipamide and polyhexamethylene isophthalamide, the latter being present in the range of from 59% by weight of the copolymer.

4. A high shrinkage, dye receptive filament consisting essentially of a copolymer of polyhexamethylene adipamide and polyhexamethylene isophthalamide, said copolymer containing more than by weight of the adipamide.

5. The filament of claim 4 wherein said copolymer contains more than 4% by weight of the isophthalarnide.

6. A drawn nylon filament comprising at least two continuous adhered components, one of said components consisting essentially of a homopolyamide, another component consisting essentially of a copolymer of polyhexamethylene adipamide and polyhexamethylene isophthalamide, there being less than 10% by weight of the isophthalamide in the copolymer.

7. The filament of claim 6 wherein the isophthalamide is present in the range of from 59% by Weight of the copolymer.

8. A drawn nylon filament comprising a copolymer of polyhexamethylene adipamide and polyhexamethylene isophthalamide, there being less than 10% by weight of the isophthalamide in the copolymer.

9. The filament of claim 8 wherein the isophthalamide 15 6 is present in the range of from 5-9% by weight of the copolymer.

References Cited in the file of this patent UNITED STATES PATENTS 2,742,496 Lum et al Apr. 17, 1956 2,931,091 Breen Apr. 6, 1960 2,965,616 Caldwell et a1. Dec. 20, 1960 FOREIGN PATENTS 873,983 France Apr. 13, 1942 OTHER REFERENCES Edgar et al.: J. Poly. Sci., vol. 8, 1952, pp. 15-19. Evans et al.: J .A.C.S., vol. 72, 1950, pp. 2024-2028. 

1. A DRAWN NYLON FILAMENT CONSISTING ESSENTIALLY OF A COPOLYMER OF POLYHEXAMETHYLENE ADIPAMIDE AND POLYHEXAMETHYLENE ISOPHTHALAMIDE, THERE BEING LESS THAN 10% BY WEIGHT OF THE ISOPHTHALAMIDE IN THE COPOLYMER.
 6. A DRAWY NYLON FILAMENT COMPRISING AT LEAST TWO CONTINUOUS ADHERED COMPONENTS, ONE OF SAID COMPONENTS CONSISTING ESSENTIALLY OF A HOMOPOLYAMIDE, ANOTHER COMPONENT CONSISTING ESSENTIALLY OF A COPOLYMER OF POLYHEXAMETHYLENE ADIPAMIDE AND POLYHEXAMETHYLENE ISOPHTHALAMIDE, THERE BEING LESS THAN 10% BY WEIGHT OF THE ISOPHTHALAMIDE IN THE COPOLYMER. 